Virtually every IC fabrication process contains an aluminum metallization step and an aluminum etching step. The aluminum serves as an interconnection layer for all of the devices on the substrate (commonly IC devices are formed on silicon or sapphire substrates which typically have a circular form and are called "wafers" or "chips"). The aluminum etching step is for the purpose of creating patterns in the aluminum layer according to a predetermined image. The aluminum layers are imaged by the use of resists which are processed to serve as etching masks. Aluminum can be imaged with positive or negative resists, but positive resists are generally preferred for better image dimensional control. An aluminum metallization layer may be etched by means of either wet or dry etchants. In recent years, plasma etching has been rapidly supplanting wet etching in IC production technology.
Unfortunately, the typical IC fabrication process is handicapped by the fact that the aluminum layers on the substrates are vulnerable to corrosion after undergoing plasma etching. The corrosion is a consequence of the materials used in plasma etching. Plasma etching of aluminum may be conducted with various materials. The most common plasma etching system for etching aluminum on silicon IC devices employs a mixture of SiCl.sub.4 and Cl.sub.2 gases, usually in the presence of an inert gas such as argon or helium. In a plasma etching step utilizing the foregoing mixture, AlCl.sub.3 is commonly formed as a reaction product. SiCl.sub.4, Cl.sub.2 and AlCl.sub.3 are all highly reactive in the presence of moisture, reacting with moisture to form highly corrosive HCl which will rapidly corrode aluminum, even at ambient temperatures and pressures. After a typical plasma etching of aluminum has occurred, at least a portion of one or more of the reactive gases SiCl.sub.4, Cl.sub.2, and AlCl.sub.3 tends to be adsorbed on the surfaces of the chip or wafer. These reactive materials are adsorbed on all surfaces of the chip or wafer, i.e., they are adsorbed on all exposed surfaces of the substrate or of materials on the substrate, e.g., on surfaces of the aluminum or any residual resist, or any other coatings (such as glass or SiO.sub.2), on the substrate.
In current high production IC fabrication processes, the wafers or chips being processed move continuously from one stage to another, and typically the wafers or chips are subjected to further processing relatively soon after aluminum etching has occurred. However, even relatively short exposure of the wafers to moisture in the surrounding environment will cause the adsorbed reactive gases to form HCl, and as a consequence, HCl corrosion of the aluminum layers on the wafers will occur at a very high rate. In such event, the corrosion may render the resulting devices on the wafers inoperative, or unacceptable, or unreliable.